In a portable, hydraulically operable tool (with accumulator or mains cable) that can be used, for example, as cable lug press, a well-known hydraulic drive is used whose switching valve with working power/pressure control function (the latter by an integrated pressure control valve) is disposed in a discharge channel to the tank which branches off from a working line from the pressure source to the hydroconsumer. When the tool is started for the first time, the working power is limited by opening the pressure control valve via the pressure control function when a working position is reached. The pressure control valve then remains in its open position, so that, after the pressure source has been switched off, the permanently acting force (either a spring or a load) will move the hydroconsumer via its return stroke to a predetermined end position and in the process allow the pressurizing agent to flow off from the admission chamber to the tank through the switching valve which is in the passage position. Then, the pressure control valve returns to its original position. Since the switching valve also controls the pressure control function, it needs a high spring force and a relatively narrow throttle point, which on the one hand requires at least one very large pressure admission surface, and on the other hand results in a relatively limited return stroke speed. The hydroconsumer will always drive back to its end position over the complete return stroke, even if the pressure source is switched on again during the return stroke. The return stroke could only be manually stopped by actuating a manual emergency device. However, this requires complicated hand movements and a considerable expenditure of force. Since the hydroconsumer always performs the complete return stroke, a lot of time is wasted until the next operation, also due to the slow return stroke speed. For in many applications, it would be sufficient, for example when cable lugs are pressed, to only slightly release the tool application controlled by the hydroconsumer until it can be transferred to a new working position without having to accept the long duration for the return stroke. The large pressure admission surface in the switching valve results in high structural efforts. Furthermore, a relatively high permanent force (energy storing spring) for the hydroconsumer is required.
It has been suggested in practice to additionally dispose an electrically operable valve in the hydraulic drive of such a tool by which the return stroke of the hydroconsumer can be stopped at any arbitrary point before the hydroconsumer has reached its end position. However, this involves additional, cost-intensive efforts and an extra demand of electric energy, being a disadvantage, for example, in a tool powered by an accumulator. Moreover, an electric activation of the valve is required, and also a separate actuator for the valve, thus rendering the handling of the tool difficult and creating additional sources of failure.